The present invention relates to a method of regeneration of plastics material with higher quality from scrapped plastics products and, more particularly, to a method of regeneration of plastics material from scrapped plastics products, of which the surface layer has been deteriorated by ultraviolet rays etc., under removal of the deteriorated surface layer by erasing it off.
Plastics products, in particular, for packing purposes such as pallets, containers and so on, have found their use in the field of transportation in a vast magnitude, and thus, they are used today in an approximate order of 10.sup.8, which has been shown to tend to increase every year. Such products as pallets etc., are used under exposure to weather, so that they exhibit decrease of the strength after a long term utilization due to deterioration of the surface layer by exposure to ultraviolet rays. While it is assumed, in general, that the allowable life of pallets and the like is about 10 years or so, those which have been destroyed by impact or clash or those which are derogated in appearance by staining by such as coal tar etc. are scrapped before 10 years' life has elapsed. Accordingly, there are today a large amount of scrapped plastics products such as pallets and so on.
Heretofore, scrapped plastics were regenerated by separating them into each individual material, crushing them by a crusher and then melting them to subject them to molding again. However, plastics scrap of such as pallet etc. exhibits on the surface thereof a deteriorated skin layer due to irradiation of ultraviolet rays and other difficultly removable layers of, for example, printing inks and greasy material such as coal tar etc. (which are referred to hereinafter as "surface deterioration layer etc."). Hence, by the previous method mentioned above, the surface deterioration layer etc. can be removed only to a minor degree during the process of disintegration of the scrapped plastics and eliminated through a separating apparatus such as a cyclone separator, screening separator and so on. Thus, most scrapped plastics will be melted with the surface deterioration layer etc. retained on them without being scraped off and the so obtained melt is molded again to regenerate the plastics.
Further, there has been proposed a method for removing obstacles adhered firmly on the surface of the vessel, in which scrapped plastics vessels are subjected to a high velocity fluidization in water or hot water, so as to remove the obstacles, such as paper labels, aluminum foils and so on, from the vessel under the utilization of frictional force due to the high velocity flow of fluid (see Japanese Patent Laying Open No. 125582/1977). This method however does not permit to removal of the surface deterioration layer etc.
Thus, plastics products regenerated from scrapped plastics by the prior methods contain obstacle materials derived from, for example, the surface deterioration layer etc., so that they can be used only for applications where lower quality of the product can be tolerated. They have thus been utilized heretofore only for construction materials which are cheap and low quality, such as for example, substitutes for tubes and plates made of concrete, blocks as substitutes for bricks and so on.
For these reasons, there have been attempted various methods for removing the surface deterioration layer etc. in a mechanical and chemical manner, in order to improve the quality of the regenerated products, with the result of no practical application yet today due to economic reasons.
As explained above, the effective utilization of resources and the prevention of environmental pollution have not been realized in sufficient manner, because of the limited application of the regenerated plastics materials.